2:53 PM PT -- We've learned Debbie's condition when she was taken to the hospital was listed as "fair to serious."

Debbie Reynolds just suffered a medical emergency, which we're told is a possible stroke ... and EMTs just raced to the scene, TMZ has learned.

Debbie was at her son Todd Fisher's home in Beverly Hills and just after 1 PM someone from the house called 911.

We're told 84-year-old Debbie, whose daughter, Carrie, died Tuesday, has been distraught since Carrie's emergency Friday on a United jet.

Family sources tell us they called 911 to report a possible stroke.

The ambulance just took Debbie to a nearby emergency room.

Debbie was at Todd's house discussing funeral plans for Carrie.

Joely Fisher, Carrie's half sister, posted a pic of her and Debbie Wednesday afternoon with the caption, "God speed mama."

Story developing ...